Cutting oils and cutting liquids represent a common type of industrial lubricating agents which are widely used in the engineering industry in connection with cutting, turning, drilling, grinding and similar machining of materials. Their primary function is to increase the useful life of the tools by acting as a cooling and lubricating agent between the tools and the work pieces. Cutting oils--as well as lubricating agents in general--consist of so-called base oils, which may be based on mineral oils or be synthetic or semi-synthetic. By "cutting liquids/lubricating liquids we mean aqueous emulsions of cutting oils and lubricating oils respectively.
Rapid microbial growth, primarily of bacteria but also of fungi, often restricts the useful life of the cutting liquids to a few months. Already after such a short time of use the bacterial concentration may have increased from zero to the order of 10.sup.8 cells/ml. The growth of microorganisms not only results in a deteriation of the properties of the cutting liquid, but also creates an unpleasant odour. In connection with e.g. grinding and turning also airborne bacteria can be spread in aerosol form, thereby creating a further problem in the working environment.
Cutting liquids contain a plurality of components, from bactericidal preparations to anti-foam agents and corrosion inhibitors. Several of these components, together with a micro-flora of bacteria and fungi, are considered to be capable of causing problems, especially eczema and skin irriation, for industrial workers (Wahlberg, J. E. 1976, Skin-influence of oil, Esso Symposium 1976).
Since no practically/economically useful methods presently are available for cleaning the cutting liquid when in use, the microbial contamination is usally coped with by simply discarding the entire contaminated cutting liquid and replacing the same with fresh cutting liquid. This procedure does not only cause high costs for the disposal and for the fresh cutting liquid, but it also creates high extra costs caused by the shut-down which is necessary for emptying and cleaning the tanks and the distribution systems for the cutting liquid and for re-filling the systems with fresh cutting liquid.
Microbial growth in cutting liquids is thus a great problem in today's engineering industry and there is a great need of means for extending the useful life of cutting liquids. It may as an example be mentioned, that about 10,000 tons of cutting liquids in 1977 were used only in Sweden, of which about 2,000 tons were emulsion concentrates (LO:s Report on Cutting Oils). The costs for the acquisition and disposal were estimated to be of the order of 140 to 200 millions SEK, to which should be added the far higher costs for shut-down in connection with the exchange of cutting liquid.
Similar problems with microbial contamination occur when using and disposing of other types of lubricating oils, for example different kinds of hydraulic oils, used oils, etc.
Derwent Abstract No. 76-65593x/35, JP 51079959 discloses an agent for the treatment of contaminated waste water, including used cutting oil, by adsorption of the contaminants. The adsorbent consists of very small complex bodies comprising inorganic particles and an organic polymer. The inorganic particles may consist of active carbon or certain metal hydroxides.
Aqueous polymeric two-phase systems as such have been known for a long time and have been used in laboratories for biochemical and microbiological analyses and separations, e.g. for separating macro molecules, cell particles and whole cells (e.g. Albertsson P. .ANG.. 1960, Partition of Cell Particles and Macromolecules, 2nd edition, Almquist & Wiksell, Uppsala; Blomquist G. and Strom G. 1984, The Distribution of Mould Fungi Conidies in Polymeric Two-Phase Systems, Work and Health No. 31, Strom G. 1986, Qualitative and Quantitative Analysis of Microorganisms Particularly Fungal Spores-Methodological Developments, doctor's thesis, University of Ume.ang.). However, polymeric two-phase system have found few technical uses.
Polymeric two-phase systems substantially consist of two aqueous solutions of polymers having different molecular weights. When the two polymer solutions are mixed in certain proportions, two immiscible aqueous phases are formed. The top-phase substantially contains the low molecular polymer and the bottom-phase substantially contains the high molecular polymer. The water contents in the systems is high, usually between 80-98% depending on the choice of the phase polymers. In an alternative type of polymeric two-phase systems basically the same result can be obtained by replacing the high molecular polymer with a suitable water-soluble salt, e.g. phosphate buffer.
In polymeric two-phase systems particles or cells are distributed substantially between the top-phase, the interphase (the interface between the phases) and the bottom-phase; soluble macromolecules will be distributed between the top and bottom-phases.
In order to simplify the description we will in the following use the expressions "top-phase component" and "bottom-phase component" respectively when referring to those component/components of the polymeric system, which after mixing and separation of the system substantially are found in the top-phase and the bottom-phase respectively.